Control circuits



Nov. 17, 1936. I v, RQSENE 2,060,898

CONTROL CIRCEIITS Filed Dec. 1, 1954 2 Sheets-Sheet l /N VE N TOR By 145. ROSENE ATTORNEY NOV. 17, 1936. v ROSENE 2,060,898

CONTROL CIRCUITS Filed Dec. 1, 1934 2 Sheets-Sheet 2 INVENTOR I! E. ROSENE A T TORNE V Patented Nov. 17, 1936 UNITED STATES PATENT ()FFICE Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application December 1, 1934, Serial No. 755,560

c 12 Claims. (Cl. 178-44) This invention relates to control circuits and particularly to control circuits for varying the attenuation on signal transmission lines.

One object of the invention is to provide a con trol circuit having a gas-filled space discharge device biased near the breakdown point and connected to a source of alternating current by a circuit tuned a few cycles off the normal frequency of the source that shall vary the frequency of said source and the tuning of said tuned circuit relatively to each other to control the operation of said device.

Another object of the invention is ,to provide a control circuit having two gas-filled space discharge devices, each biased near the breakdownv point and respectively connected to a source of alternating current by two circuits, each tuned a few cycles off the normal frequency of the source that shall selectively operate said devices by varying the tuning of said tuned circuits.

the breakdown point, and a source of alternating current connected to said devices by two tuned 35 circuits each tuned off the normal frequency of the source by,a few cycles that shall vary the frequency of said source and the tuning of said tuned circuits relatively to each other according to the operation of said galvanometer to govern 40 the attenuation on a linecircuit.

The attenuation of a signal transmission line varies according to various conditions as, for example, temperature and corrections must be made for attenuation variations to insure eflicient 45 transmission of signals. According to the present invention, means are provided under control of a pilot frequency current for controlling gas-filled space discharge devices to govern the attenuation on the transmission line.

50 The present invention is illustrated by means of a carrier wave transmission system. Signals are transmitted. in one direction by means of carrier waves lying within one frequency range and are transmitted in an opposite direction by 55 carrier waves lying within another frequency range. The attenuation of the line is controlled in accordance with the energy level of pilot frequency currents which are transmitted at a constant energy level at one station and received at the other station at a level depending on the 5 line attenuation.

In the illustrated carrier current system, a plurality of carrier currents lying within one frequency range are employed for transmitting signals in one direction. A pilot frequency lying 10 within the same frequency range as the carrier currents is employed for controlling the attenuation of the line at a' distant station. A plurality of carrier currents lying within a different frequency range are employed at the distant sta- 15 tion for transmitting signals to the first mentioned station. A pilot frequency current lying -within the second frequency range is employed for controlling the attenuation of the line at the first'mentioned station.-

The pilot frequency current which is employed at the distant station for controlling the line attenuation is selected from the various carrier currents-by means of a filter, is rectified and employed for controlling a galvanometer. The galvanometer carries a small plate which is preferably composed of aluminum for controlling two variable condensers respectively connected to two tuned circuits. The two tuned circuits serve to connect the input circuits of two gas-filled space discharge devices to the oscillator supplying the pilot frequency current at the distant station. The term gas when used in the expression gasfilled tube in the specification and claims is employed in its broad sense and is intended to include vapors. A separate oscillator may be employed in place of the pilot frequency oscillator. The two gas-filled space discharge devices arebiased to very near their breakdown points so that they may be easily operated by means of the two tuned circuits under control of the galvanometer. The two tuned circuits are tuned a few cycles off the frequency of the oscillator connected thereto. The coil of the galvanometer when moved in one direction controls one variable condenser to tune the tuned circuit associated therewith to the frequency of the pilot oscillator. The coil of the galvanometer when moved iii an opposite direction controls the other variable condenser to tune the second tuned 60 circuit to the frequency of the pilot oscillator. Each of the tuned circuits when tuned exactly to the frequency of the pilot oscillator supplies sufficient potential for breaking down one of the gasfilled space discharge devices. The gas-filled I space discharge devices control relays to operate a control motor in a forward and in a reverse direction. The control motor operates an equalizing switch which, in turn, controls an. attenuation equalizer in the line at the distant station.

The control motor also operates a centering cam to stop the motor and equalizing switch at the proper point.

In a system constructed as above indicated, the galvanometer is operated in accordance with the energy level of the pilot frequency current received at the distant station. The galvanometer, when operated, serves to control one or the other of the variable condensers for tuning one of the tuned circuits to the frequency of the pilot oscillator. The. tuned circuits selectively operate one of the space discharge devices for operating the control motorin a forward or in a reverse direc tlon. The control motor, by means of the equalizer switch, controls the attenuation equalizer to compensate for the change in attenuation of the line between stations. The change in the attenuation equalizer restores the galvanometer to its normal position."

lator may be provided at a station which is distinct from the pilot oscillator at that station.- Thefrequency of the current generated by the local oscillator is controlled by a galvanometer which is governed according to the energy level of the pilot frequency current received at that station. The galvanometer controls the frequency of the local oscillator by means of a variable condenser. The local oscillator is connected to two gas-filled space discharge devices by means of twotuned circuits. One of the tuned circuits is tuned to a frequency slightly above the normal frequency of the local oscillator and the other tuned circuit is tuned to a frequency slightly below the normal frequency of the local oscillator.

The two space discharge devices are biased to near their breakdown points so that when the local oscillator frequency is changed to the frequency of one or the other of the tuned circuits, operation of one of the space discharge devices takes place. The space discharge devices control relays which, in turn, operate a control motor in a forward or in a reverse direction. The control motor governs an equalizing switch which in turn operates an attenuation equalizer in the line at the station.

The control motor also operates a centering cam to stop the motor and equalizing switch at the proper point.

In the accompanying drawings, Figs. 1 and 2 taken together diagrammatically illustrate a carrier current transmission system provided with control circuits constructed in accordance with the invention.

Referring to the drawings a signal station I is connected to a distant signal station 2 by means of a line comprising conductors 3 and 4. The signal station I shown in Fig. 2 of the drawings com,- prises a receiving channel 5 and a transmitting channel 8. The transmitting channel 6 is connected to the transmission conductors 3 and 4 by means of high-pass filters I and 8. The receiving channel 5 is connected to the transmission consion in one direction and a plurality of carrier (not shown) is connected to the circuits II), I I and I2 for modulating carrier current waves with speech or other signals. An oscillator I5 having a frequency within the frequency range of the carrier currents passed by the filters I3, I4 and I5 is connected to the channel 6 for controlling the attenuation of the line at the distant station 2. A suitable amplifier I1 is provided in the channel 6.

The receiving channel 5 at station I comprises besides the attenuation equalizer l8 and the lowpass filter 3 for passing the lower frequency range of carrier currents transmitted from the distant station 2, an amplifier I9. Suitable filters 20, 2|

and 22 which are connected to the receiving channel 5 select the carrier currents within the lower frequency range that aretransmitted from the. In another form of the invention a local oscildistant station. The filters 20, 2i and 22 are connected respectively to receiving circuits 23, 24 and 25. Attenuation control circuits 25 are provided at the station I for controlling a switch 21 to adjust the attenuation equalizer l8. The attenuation control circuits 26 will be described in detail later.

The station 2 shown in Fig. 1 of the drawings comprises a transmitting channel 28 and a receiv ing channel 29. The transmitting channel 25 comprises an amplifier 3| and a low-pass filter 30 which passes the carrier currents located within the lower frequency range that are employed for transmission in one direction to the station I.

' Transmitting circuits 32, 33 and 34 including carrier current apparatus (not shown) are connected I to the transmitting channel 23 by means of filters 35, 35 and 31. The filters 35, 35 and 31 select carrier waves within the lower frequency range. A pilot oscillator 38 is connected to the transmitting channel 23 for controlling the attenuation control circuits 25 at the station I.

The oscillator 33 has a frequency within the lower frequency range.

The receiving channel 29 at station 2 comprises a high-pass filter 39 which passes carrier currents located within the higher frequency range, an

" galvanometer 50 governs the operation of a motor 5| for controlling the setting of the attenuation equalizer 40. I

Two tuned circuits 52 and 53 are respectively connected to the input circuits of two gas-filled tubes 54 and 55. Plate potential for the two gasfilled tubes 54 and 55 is supplied by a battery H2. The tube 54 directly controls the operation of a relay 55 having armatures I02 and I03. The tube 55 directly controls the operation of a relay 51 having armatures I04 and I05. The relay 55 controls a relay I which in turn controls the operation of the motor i in one direction. The relay 51 controls a relay I iii which in turn controls the operation of the motor 5| in a reverse direction. The motor 5i comprises an armature 53 and two field windings 59 and 53.

The tuned circuit 52 oompriau a aecomhry 3,060,898 winding 6I of a transformer 62 and an adjustable condenser 63. The tuned circuit 53 comprises a secondary winding 64 of the transformer 62 and an adjustable condenser 65. The primary winding of the transformer 62 is connected through a filter 66 to the pilot oscillator 38 of station 2. The filter 66 selects current having the frequency of the pilot oscillator 38. Each of the tuned circuits 52 and 53 is tuned a few cycles off the frequency of the pilot oscillator 38 and the two space discharge devices 54 and 55 are biased by the battery 61 to near their breakdown points. Thus, the gas-filled tube 54 and the gas-filled tube 55 may be easily broken down if the circuit 52 or the cir-' cuit 53 is tuned to the frequency of the oscillator 38.

A shaft I20 which connects the motor 5I to the switch arm I5 carries a centering cam member I4. The centering cam member I4 serves to stop the operation of the motor 5| when the equalizer switch I5 has reached thecenter of a contact position. Notches are formed in the periphery of I grounded contact arm I23 and holds the grounded contact arm out of engagement with a contact member I24. When the projection on the contact arm I6 rests on a projection between two notches in the cam member I4 the grounded contact arm I23 engages the contact member I24 and disengages the contact arm I6.

The galvanometer arm 68 carries a plate 69 which may be moved adjacent to a stationary plate I and a stationary plate II. The plate 69 is connected to a common terminal of the condensers 63 and 65 in the tuned circuits 52 and 53. The plate I0 is connected to the opposite terminal of the condenser 63 and the plate II is connected to the opposite terminal of the condenser 65. If

the galvanometer is operated to move the plate 69 adjacent to the plate I0 the tuning of the tuned circuit 52 is changed to the frequency of the pilot oscillator 38 for operating the gas-filled space discharge device 54. If the plate 69 is moved adjacent to the plate II the circuit 53 is tuned to the frequency of the oscillator 38 and the gasfilled space discharge device 55 is operated.

The pilot frequency current received at station 2 from the oscillator I6 at station I operates the galvanometer 50 according to the strength of the current received. Assume that the plate 69 is moved adjacent the plate I0 in case the pilot current strength is low and that the plate 69 is moved adjacent the'plate II in case the strength of the pilot frequency current is high. Thus, in case the pilot frequency current strength is low the circuit 52 is tuned for operating the device 54. The operation of the device 54 effects operation of the relay 56. The relay 56 by means of the armature I02 completes a circuit for operating the relay I00. The relay 56 operates the armature I03 for completing a holding circuit that includes the contact arm I6 and the grounded contact arm I23. The relay I00 completes a circuit by means of the armature I I0 for energizing the armature 56 and the field winding 59 of operating the relay 51.

the motor from the source 13. The motor 5I and the equalizer switch I5 connected thereto are rotated in a direction to lower the loss in the attenuation equalizer 40. The armature I09 of the relay I 00 breaks the operating circuit of relay 56 and insures the breaking of the circuit through the gas filled device 54. The armature II I of the relay I00 prepares a holding circuit for the relay I00 that is completed when the grounded switch arm I23 engages the contact member I24.

When the projection on the contact arm I6 is moved by-the rotation of the cam member I4 to a position between two notches in the cam member the holding circuit for the relay 56 is broken and the holding circuit for the relay I00 is completed by the grounded contact arm I23 engaging the contact member I24. The relay I00 serves to hold the circuit of the motor 5 closed until the projection on the contact arm I6 enters the next notch in the cam member I4. The attenuation switch I5 will be moved to the next position when the projection on the contact arm enters the next notch. The holding circuit for the relay I00 is opened when the grounded contact arm I23 disengages the contact member I24. The release of the relay I00 opens the circuit of the motor 5|. The equalizer switch I5 in moving from one position to an adjacent position changes the loss of the attenuation equalizer 40 so that the galvanometer 50 is restored to its nor- 7 mal position. Therefore the closing of the plate circuit of the gas-filled space discharge device 54 by the releasing of the relay I00 will not cause the relay 56 to be reoperated.

If the strength of the received pilot frequency current is high, the plate 69 is moved adjacent to the plate II for tuning the circuit 53 to the frequency of the oscillator 38. When the circuit 53 is tuned to the frequency of the oscillator 38, the space discharge device 55 is broken down for The relay 51 operates the armature I05 to complete a circuit for operating the relay IOI. The relay II by means of the armature I08 completes a circuit from the battery 13 for energizing the armature 50 and the field winding 60 of the motor 5|. The motor 5I is rotatedin a reverse direction to increase the loss in the equalizer 40. g

The cam member I4 operates the contact arm I6 to disengage the grounded contact arm I23 when the motor is rotated as above set forth. The separation of the contact arms I23 and 16 opens the holding circuitfor the relay 51. The relay 51 opens the circuit for the relay IOI through the armature I05. The relay IOI is held closed how- .ever by a circuit completed by the grounded contact arm I23 engaging the contact member I 24. When the projectionon the contact arm 16 enters the next notch on the cam member I4 the contact arm I6 moves the grounded switch arm I23 out of engagement with the contact member I24 for releasing the relay IOI to stop the motor 5i Referring to Fig. 2 of the drawings the attenuation control circuit 26 may be similar in construction and operation to the attenuation control circuits employed at station 2 if so desired.

.The control circuits 26 shown in Fig. 2 of the cillator 88 at station 2. The galvanometer 88 controls the frequency of a local oscillator 88. The

local oscillator 83 is connected to two gas-filled space discharge devices 84 and 88 by means of two tuned circuits 88 and 81. The circuit 88 is tuned a few cycles above the normal frequency of the oscillator 88 and the circuit 81 is tuned a few cycles below the normal frequency of the. oscillator 88. The two space discharge devices 84 and 88 are biased by the battery 88 to near their break down point so that when the oscillator 88 produces a frequency corresponding to the tuning of the circuit 88 or the circuit 81, one or the other of the space discharge devices 84 and 88.13 broken down.

The device 84 controls a relay 88 which in turn on the arm I28 is in a notch on the cam member.

When the contact arm I28 is moved out of engagement with the grounded contact arm I21 by the cam member 88 the arm I21 engages the contact member I28.

The device 85 controls a relay 88 which in turn controls a relay 88. The relay 88 completes a circuit from the battery 84 through armature 88 and the field winding 82 of the motor at station I. The motor at station I when controlled by the device 88 operates in a reverse direction. The relays 88 and 88 are similar in construction and operation to relays 58and81' at station 2 and the relays 81 and 88 are similar in construction and operation to the relays I88 and IM at station 2.

The galvanometer 88 is operated according to the strength of the received pilot current for tuning the local oscillator "to the frequency of one of thetuned circuits 88 and 81 for selectively operating the gas-filled space discharge devices 84 and 85. The gas-filled space discharge devices 84 and 88 operate the motor 88 in a forward or reverse direction by meansof the relays 88 and 81 or 88 and 88 for correcting the loss on the attenuation equalizer I8 by means of the switch 21.

Modifications in the system and in the arrangement and location of parts may be made within the spirit and scope of the invention and such modifications are intended tobe covered by the appended claims. 7

What is claimed is:

1. In combination,- two gas-filled space 'discharge devices each biased near the breakdown point, a source of alternating current, two tuned circuits normally tuned off the frequency of said source, said circuits respectively connecting, the devices to said source, and means for varying the frequency relationship between said source and said tuned circuits to selectively operate said devices.

2. In combination, a gas-filled space discharge device biased near the breakdown point, a source of alternating current, a circuit tuned a few cycles off the normal frequency of said source, said circuit connecting the device to said source, and means for varying the frequency relationship between said source and said tuned circuit to control the operation of said device.

3. In combination, a plurality of gas-filled space discharge devices each biased near the breakdown'point, a source of alternating current, a plurality of tuned circuits normally tuned off the frequency of said source, said circuits respectively connecting the devices to said source, and means for varying the frequency relationship between said source and said tuned circuits to selectively operate said devices.

4. In combination, space discharge devices each biased near the breakdown point, a source of standard frequency current, a plurality of. circuits tuned a few cycles of! the frequency of said source and respectively connecting the devices to said source, and means for varying the tuning of said circuits to selectively operate said devices.

5. In combination, a source of standard frequency current, two .tuned circuits connected in parallel to said source and each tuned a few cycles oif'the frequency of said source, two gas-filled space discharge devices connected respectively to said tuned circuits and biased near to the breakdown point, and means for varying the tuning of said circuits to selectively operate said devices.

6. In combination, two gas-filled space discharge devices each biased near the breakdown point, a source of alternating current, two tuned circuits connected in parallel between said source and said devices, said circuits being each tuned a few cycles off the frequency of said source, and means comprising two variable condensers respectively associated with said circuits for varying the tuning of said circuits to selectively operate said devices.

-8. In combination, two gas-filled space dir charge devices each biased near the breakdown point, a source of alternating current, a circuit tuned a few cycles above the normal frequency of said source, a circuit tuned a few cycles below the normal frequency of said source, said circuits respectively connecting'the devices to the source, and means for varying the frequency of said source to selectively operate said devices.

9. In combination, two gas-filled space discharge devices each biased near the breakdown ,point, a source of alternating current, a circuit tuned a few cycles above the normal frequency of said source, a circuit tuned a few cycles below the normal frequency of said source, said circuits respectively connecting the devices to the source, and means comprising a variable condenser for controlling the frequency of said source to selectively operate said devices.

10. In a carrier wave transmission system, a line having a variable attenuation, means for transmitting signals over said line by means of carrier waves, means for transmitting a pilot frequency current from one station to control the attenuation at a distant station, a galvanometer at the distant station, means for operating said galvanometer according to the energy level of the pilot current at the distant station, two gasfllled space discharge devices at the distant station each biased near the breakdown point, a source of alternating current, two tuned circuits each tuned a few cycles of! the frequency of said source, means comprising two variable condensers a plurality of gas-filled controlled by said galvanometer for governing said tuned circuits to operate one of said devices when the energy level of the pilot current is above normal value and to operate the other device when the energy level of the pilot current is below normal value, and means controlled by said devices for governing the line attenuation at the distant station.

11. In a carrier wave transmission system, a line having a variable attenuation, means for transmitting signals over said line by means of carrier waves, means for transmitting a pilot frequency current from one station to control the attenuation at a distant station, a galvanometer at the distant station, means for operating said galvanometer according to the energy level of the pilot current, two tuned circuits connected to the input circuits of two gas-filled space discharge devices at the distant station, an oscillator connected to said tuned circuits, each of said circuits being tuned a few cycles oh. the frequency of said oscillator and said devices being biased near the breakdown point, means controlled by said galvanometer for controlling said tuned circuits to operate one of said devices when the en--' ergy level of the pilot current is above normal value and to operate the other device when the energy level of the pilot current is below normal value, and means controlled by said devices for governing the attenuation at the distant station.

12. In a carrier wave transmission system, a line having a variable attenuation, means for transmitting signals over said line by means of carrier waves, means for transmitting a pilot frequency current from one station to control the attenuation at a distant station, a galvanometer at the distant station, two gas-filled space discharge devices at the distant station each biased near the breakdown point, an oscillator, a circuit tuned a few cycles above the frequency of said oscillator, a circuit tuned a few cycles below the frequency of said oscillator, said circuits respectively connecting the devices to said oscillator, means comprising a variable condenser controlled by said galvanometer for controlling the frequency of said oscillator to selectively operate said devices according to the line attenuation, and means controlled by said devices for governing the attenuation at the distant station.

VICTOR E. ROSENE. 

